Acoustic device



May 6, 1930.

H. C. HARRISON ACOUSTIC DEVICE Filed July 3l, 1926 4 Sheets-Sheet 1 www lmw May 5, 1930- H. c. HARRISON 1,757,712

ACOUSTIC DEVI CE Filed Jul},T 3l, 1926 4 Sheets-Sheet 2 fiyf May 6, 1930. H. c. HARRISON f 1,757,712

f ACOUSTIC DEVICE Filed'July 31, 192e 4 sheets-Sheet 4 Patented lMay 6, 1935 UNITED 'STATES lliit'ralar OFFICE EENRY 0.HARRrsoN, 0E PORTWASHINGTON, NEW YORK, lAssIaNoR To BELL TELE- PHONE LABORATORIES, INCORPORATED, OE NEW YORK, N. Y., A CORPORATION OF NEW l,YORK

Application mea July 31,

This invention relates to acoustic devices and particularly to horns -for phonographs, loud speaking' telephones and the like.

vAn object of the invention is to obtain compactness in acoustic instruments.

body in a phonograph cabinet of about A further objectof the invention is to ein#l uniformly transmit Waves of all frequencies above a definite critical frequency determined f by the rate of taper and will efficiently radiate all Waves whose Wave lengths are not greater than 3 to 4L times the equivalent diameter of the mouth or bell opening. In order to etticiently radiate into the atmosphere sound Waves of frequencies in the lower portion of the music range, it is necessary to use a horn having a. lengthof about 13 ft. and a mouth opening equal, narea to that of a circle of about 4 ft. diameter. In order to mount a horn ofv such dimension in an ordinary phonograph cabinet,- it is necessary to provide a tortuous passage, for example of the type described in the application of H. C. Harrison referred to above.. i However, it has been found that reflection losses are produced by sharply bending' a passage of large area.

. In accordance With this invention the horn passage is bent without the introduction of reflection losses, by dividing the passage into a large number of small passages so thatl the area of any sharply bent passage is comparatively small.

In a preferred embodiment of this invention a phonograph is constructed having a horn comprising a b ell portion divided by a partition in which is located a pluralityv of folded horn passages arranged in multiple. The folded sound passages are formed by dividing the conduit leading from the tone arm so that it leads to .two sections located respectively in thev upper and lower portions of the dividing partition.l Each of these sections contains two spirally expanding passages,

' v ACOUSTIC DEVICE 1926. Serial No. 126,312.

each of which leads to a sound passage in the central portion of the partition which is also connected to the corresponding spiralpassage in the other portion of the partition.

' Each of these central passages is divided by vmeans of a heart-shapedpartition to form expanding passages Which lead to the rear end of the partition Where they open into the bell lportion of the horn. The Walls of the upper portion of the bell are hinged so that they may be folded to form a cover for the phonograph cabinet, and the turn-table and driving mechanism are mounted on the dividing partition. l

Obviously the various features of this prie` ferred en'ibodiment may be useful 'separately or in various combinations. For example, the folded structure usedin the horn may be used in various other acoustical devices such as musical instruments; theulrornl may Vbe built With a considerably' smaller mouth opening without much sacrifice in quality,

in which case it may be builtin a phonograph' cabinet without the use of the cover as part of the horn and with the turn-tablefmountedV elsewhere than in the moith; the feature of mounting the turn-table Within the mouth or that of using a folding cover as jpart of the mouth wall may be applied to other structures; and the arrangement of overlaid horn passages may be varied in many obvious manners; all Within the limits of this invention.

In the accompanying drawing:

Fig. l is a perspective'view of a phonograph embodying the invention;

Fig. 2 is a fragmentary transverse sectional view through the device, the upper portion being taken on the plane of line 2 2 of Fig. 3 .while the lower portionis taken on the plane of line 2& 2EL of Fig. 3;

Fig. 3 is anirregular horizontal sectional view of the device;

Fig. 4 isa perspcctiveview of oneof the heart-shaped partitions;

95 Fig. 5 is a fragmentary sectional view simling the horn constructed of metal with pori tionsbroken away to `more clearly illustrate the details of construction.

Referring first to Figs. '1 to 4, there is shown a cabinet comprising a frame supporting a bottom 11, back 12 andthe sides 13 and 14. AA cover 15 lis hinged at 16 nearv the back 12 and carries twov leaves 17 and 18 which, wher open, form portions of the side walls of the upper portion of thebell or mouth of the horn.

.A-s, x illustrated, the front of the cabinet is` i 4 wholly open but maybe closed by vdoors 19 and 20 which are hinged to the front edges of I `the sides'l3 and 14.

Secured to the back 12 is-a strip 21 which is provided in its front face with a pair of horizontal vgrol s 22 and 23, separated from each other by anorizontal disposed ridgev 24 which extends Ithroughout the entire width of thecabinet. A wall 2 5 extends forwardly and downwardly from the lower edge of the strip 21 to the forward edge of the bottom lland forms the bottom wall of the bell portion of the horn. The upperwallvof the bell portion `Mountedl within the cabinet and extending longitudinally between walls 13 and 14 is a partition 27 whichis substantially heart- '-shaped in cross section anddivides the bell portion of the horn into two outwardly flaring tone chambers 28 and 29, which taper inwardly toward the back of the cabinet and vcommunicate withthe tapered passages 30 vand A31 formed between the strip 21 and the heart-shaped partition 27, as most clearly illustrated in Fig. 2'. 'The'inner or'reduced.

ends of these tapered passagesl 30 and 31 open into each other in such a manner that sound entering through passages inv the .partition will be divided upon encountering the ridge 24 so as to'be distributed'into the chambers 2 8 and 29.

i' It will be noted that the chamber 28 and passage 30 are both larger in cross 'sectional area than are the chamber 29 and passage 31. While such a'n arrangement is not essential to the proper functioning of the horn, it has been found desirable to construct horns of this character in such a manner, in order to accommodate the phonograph mechanism to be more fully described hereinafter. Furi thermore, experiment has shown that certain other desirable results may be secured'and under certain conditions the tonal qualities vof the horn will be enhanced by offsetting the heart-shaped partition 27 relative to the ridge 24.

'Intermediate i-ts upper and low-er' curvedV faces, the partition 27 is provided with a pluralit-y of longitudinal passages 38,39 and 40 ywhich openl out through the back of the partition and have innervor baclr walls formed by a curved face piece 33 provided with'perpendicular ridges 34, 35 and 36. .The curved faces formed between these ridges cooperate with the heart-shaped partitions 37 in prO- ducing the curved tapered sound passages 38, 39 and 40, the larger endsof which'communicate with the reduced ends of the passages 30 and 31through a common discharge mouth. v`

AThe heart-shaped partition `37y is best illustrated in Fig. 4, and comprises a'heartshaped body- 41 formed at its apex with oppositely-disposedarms 42 and 43 arranged in a'plane perpendicular to the plane of the body. The rear faces of these arms are curved to conform to the curvature of the grooves 22 and 23, while the front faces of the said arms are curved to conform to the curvature of, and to partiallyembrace the rear edges of the transversely heart-shaped partition 27. As illustrated, the side faces of the Y' through which sound is conducted into the passages 38, 39 and 40. Each of the passages 45 connect with substantially spiral, tapered passages 48 formed in those sections of the partition 27 which overlay and underlay the central passages 40, 38 and 39 so that each ofthe throats47 'of the central passages is connected with two spiral passages, one located in the upper section of the partition 27 and the other in the lower. Each of the spiral passages contracts in area as the spiral expands, the small ends of thetwo passages in each section of the partition joining in the passages 49 and 50, respectively which connect with the legs 51 and 52 of the conduit 54. -The conduit 54 turns upwardly as illustrated in the drawings and is connected at itsl upper end with atone arm 55 carrying at its free end a phonograph reproducer 5G. It is to be understood, however, that any type of sound reproducer may be substituted for that shown, for example a telephone receiver 57 as illustrated in Fig. 5.

4Owing to the division of the horn into a plurality of sound passages of small'area each passage may be bent at a sharp angle without creating serious reflection losses in the sound being transmitted, so that a horn of as at 58 to receive a suitable motor upon which the turn-table 59 is mounted. In this manner compactness of construction may be readily 'achieved and the whole may be en- Closed in a single cabinetof minimum size consistent with the great effectual length of the horn.

In operation it will be understood that sound introduced into the tone arm willl enter the sound conduit 54 where it will be divided and directed through the passages in the arms 53 thereof, entering the passages 49 and 50 through which it is conducted to the spiral passages 48. Passing through both the upper .and lower sets of passages 48, the sound waves from the corresponding upper and lower passages merge upon entrance into the throat 4Z, only to be again divided by the perpendicular ridges 34 and 3G and directed around the heart-shaped partitions 37 through the tapered passages 39 and 40 from the discharge mouths of which they are directed rearwardly against the ridge Q4 and divided sogas to enter the passages 30 and 3l y from whence they expand out through the K tone chambers Q8 and 29-of the bell portion of` the horn.

The tortuous course pursued by the sound waves is such as to permit of the construction of a horn of great edectual length, allowing a slow taper from a small throat to a large mouthopening, in a cabinet of mod erate size.

In the modification shown in Fig. G, the horn is constructed of metal conduit the passaggs being arranged in a similar manner to those ofthe horn of Figs. l to 4;. The bell portion is divided into two separate expansion chambers Gland 62, by means of a pair of longitudinally disposed curved walls G3 and 64 which are bent back at their rear edges to form the horizontal walls of the central .Secured to the walls 63 and 64 adjacent their rear edges and extending rearwardly to the outer walls of the bell or flare portion 60 are pcrpendicularly disposed partitions 65, the side faces of which are tapered toward the front of the horn, similar to the arrangement in the horn previously described.

What is claimed is:

v1. A horn comprising a throat portion, a bell portion and at least three sound passages in multiple therebetween.

2. A horn comprising at least three sound i passages in multiple, said passages being sharply bent to reduce the volume occupied by.

the horn.

3. A horn having a discharge mouth, a throat, and a divided sound passage, the rate of'taper of which increases by a constant per cent per unit of length, each division of the passage being subdivided to provide thin sound conduits which are sharply curved, the sum of the cross sectional areas of'the conduits at a predetermined distance from the throat being equal to the Cross sectional area of a single passage following the same rate of hollow partition 'in said bell portion and` means for dividing the lspace within said duce the cross sectional areas of the paths' traversed by transmitted sound to a value below that at which jserious reflection loss would occur due to sharp bending.

5. A horn comprising a bell portion and means associated therewith. having a divided sound passage therein discharging into the bell portion, and having overlaid sound passages discharging into the first mentioned sound passage.

6. A horn comprising a bell portion and means associated therewith having a divided sound passage discharging into said bell portion, and'having a sound passage on each side of and discharging into the first mentioned sound passage.

7. A horn comprising a bell portion, and a partition therein having sound passages discharging into the bell portion and overlaid sound passages discharging into the first mentioned sound passages. .Y

'8. A horn comprising a bell portion," and a partition therein, said partition having sound passages communicating with the bell portion and having sound passages on opposite sides of the first mentioned .passages communicating therewith.

.9. A horn comprising a bell portion, and a partition therein, said partition havingI sound passages disposed in the plane of its longitudinal axis, and having sound passages on opposite sides of the first mentioned passages communicating therewith.

l0.l A horn comprising a bell portion, a partition dividing said bell portion into two chambers, a throat portion, and an intermediate portion located within said partition,'said intermediate portion comprising a curved passage in one plane and a'spirally curved passage in another plane.

11. A horn comprising a bell portion, a.

partition dividing said bell portion into two `first plane, both of said spiral passages having one end connected to said curved passage and the other end connected to said throat portion.

12. A horn comprising a bell portion, a

chambers, a throat portion, and an intermediate portion located within said-partition, said intermediate portion comprising two sets of-pa'ssages, each comprising two oppositely curved substantially iiat passagesand a pair of spiralpassages located oneach side of said sets of passages, one spiral passage on each side being connected with one of said sets of passages. e v

'13. A horn comprising a bell portion, a partition therein, said partition having sound passages expanding in the plane of. said partition and opening into a common discharge mouth from which sound conducted .through the passages enters the bell portion, and having sound passages on 'opposite sides of the first mentioned passages communicating therewith, and partitions perpendicular to the plane of thellirst mentioned. partition for expanding the wave front of thesound waves in both planes as they enter the bell portion.

transmitted sound -to expand in bothl planes as it enters .the bell portion.

17.' A horn comprising a throat portion, a

fbell portion, 'and an intermediate portion therebetween, said intermediate portion comprising diverging sound passages from 'said throat portion, each of said diverging sound passages being divided, said divided passages being reunited upon entering the bell portion.

partition dividing said `bell portion into two In witness whereof, I hereunto subscribe 30th day of July, A. D., 1926;

my name this HENRY (C. HARRISON.

14. A horn comprising a bell-portion, a

longitudinally grooved partition therein dividing the ibell portion into sound discharge chambers, a plurality of heart-shaped partitions extending into the groove and forming tapered sound'passages, the first 'mentioned partition being provided with sound passages communicating with the tapered sound passages, and a sound conduit through which sound is introduced into the horn.

15. A horn comprising a bell portion, a horizontally disposed longitudinally groovedv partition therein dividing said bell portion into sound discharge chambers,heart-shaped` partitions extending into the groove in the partition and forming tapered sound passages, the first mentioned partition being provided with spiral sound passages on opposite sides of the groove, said spiral passages communicating with the tapered passages, and a sound conduit having divergent legs .through which sound is conducted to the spiral passages. l

16. A'horn comprising a bell portion expanding in one plane, a partition dividing.

said bell portion into two chambers, a sound passagev within said partition expanding ina plane perpendicular to' the plane in which the bell portion Yexpands` and partitions perpendicular to said first .partitionand Wedge shaped as to'permit the wave-front of the 

